1. Field of the Invention
The present invention relates generally to a jack plate and, more specifically, to a jack plate that allows for partial disassembly of the jack plate structure without the requirement that the supported outboard motor be removed from the jack plate.
2. Description of the Prior Art
It is well known to those skilled in the art that a jack plate can be attached to a transom of a marine vessel for support of an outboard motor in such a way that the outboard motor can be raised or lowered relative to the position of the transom while the jack plate remains attached to the transom and the outboard motor remains attached to a movable portion of the jack plate. Some types of jack plates provide hydraulic devices to assist the operator of a marine vessel in raising and lowering the outboard motor by causing the movable portion of the jack plate to move relative to the stationary portion of the jack plate which is attached to the transom of the marine vessel.
U.S. Pat. No. 6,227,920, which issued to Alby et al. on May 8, 2001, discloses a fastener for attaching an outboard motor to a transom of a boat. The fastener for attaching a first component to a second component comprises an elongated opening formed in the first component with the elongated opening having a plurality of similarly shaped portions. An insert is disposable into each one of the plurality of similarly shaped portions and can be square in a preferred embodiment. Each of the plurality of the similarly shaped portions of the elongated opening is shaped to receive the insert therein. The insert is limited in  movement by the elongated opening to a direction that is perpendicular to the plane of the elongated opening. A hole is formed in the second component and a cylindrical member is disposable through the insert, through the hole, and through the elongated opening. A capture mechanism prevents the insert from moving out of the elongated opening in a direction perpendicular to the plane of the elongated opening.
U.S. Pat. No. 6,183,321, which issued to Alby et al. on Feb. 6, 2001, discloses an outboard motor with a hydraulic pump and electric motor located within a steering mechanism. The outboard motor comprises a pedestal that is attached to a transom of a boat, a motor support platform that is attached to the outboard motor, and a steering mechanism that is attached to both the pedestal and the motor support platform. It comprises a hydraulic tilting mechanism that is attached to the motor support platform and to the outboard motor. The outboard motor is rotatable about a tilt axis relative to both the pedestal and the motor support platform. A hydraulic pump is connected in fluid communication with the hydraulic tilting mechanism to provide pressurized fluid to cause the outboard motor to rotate about its tilting axis. An electric motor is connected in torque transmitting relation with the hydraulic pump. Both the electric motor and the hydraulic pump are disposed within the steering mechanism.
U.S. Pat. No. 6,146,220, which issued to Alby, et al. on Nov. 14, 2000, discloses a pedestal mount for an outboard motor. An outboard motor is mounted to a transom of a boat with a pedestal that is attached either directly to the transom or to an intermediate plate that is, in turn, attached to the transom. A motor support platform is attached to the outboard motor, and a steering mechanism is attached to both pedestal and the motor support platform. The tilting mechanism is attached to the motor support platform and to the outboard motor. The outboard motor is rotatable about a tilting axis relative to both the pedestal and  the motor support platform. The tilting mechanism is rotatable relative to the pedestal and about a steering axis. The steering axis is generally vertical and stationary relative to the pedestal and is unaffected by the tilting of the outboard motor. The tilting mechanism is rotatable relative to the pedestal and about the steering axis with the outboard motor.
U.S. Pat. No. 6,132,271, which issued to Hebert on Oct. 17, 2000, describes a jack plate for vertical and aft placement of an outboard motor. It is an apparatus for adjusting the position of a boat motor. The apparatus contains a first transom member extending perpendicular from the transom, with the first member having a first longitudinal slot therein; and a second transom member extending perpendicular from the transom, with the second member having a second longitudinal slot therein. The apparatus further includes an upper plate positioned between the first and second transom member, with the first plate being attached to the first transom member and the second transom member. Also included is a first motor bracket member slidably connected to the first transom bracket and a second motor bracket member slidably connected to the second transom bracket. The apparatus further includes a lower plate position between the first motor bracket member and the second motor bracket member, with the lower plate being attached to the first motor bracket member and the second motor bracket member. A central bolt having a threaded stem is disposed through a smooth bore in the upper plate and a threaded bore in the lower plate. A rotational force applied to the central bolt will move the lower plate. The movement of the lower plate will lower or raise the motor in relation to the boat's transom.
U.S. Pat. No. 5,782,662, which issued to Icenogle on Jul. 21, 1998, describes a hydraulic marine jack plate. The powered jack plate for use with a marine outboard motor in a marine environment is described. The inward side of the jack plate is attached to the transom of a boat. The outboard motor is attached  to the outward side of the powered jack plate. Hydraulic power is the preferred power source. Hydraulic fluid is supplied by a separate hydraulic pump. The jack plate comprises a pair of opposing supports which are interconnected by support bars. The opposing supports incorporate linear bearings in which rides a slide which is capable of vertical movement. The linear bearings are provided with grease fittings for positive lubrication. The outward side of the opposing supports is higher than the inward side, thereby permitting maximum upward travel of the slide and the linear bearings are locked into the opposing supports via an undercut groove which is integral with these supports.
U.S. Pat. Des. 372,452, which issued to Icenogle on Aug. 6, 1996, describes a marine jack plate which is attachable to a transom of a marine vessel.
U.S. Pat. No. 6,305,996, which issued to Detwiler on Oct. 23, 2001, describes a variable height outboard motor mount. A manually adjustable outboard motor mount comprises two bracket assemblies, one being attachable to a boat transom and the other being attachable to support an outboard motor. The motor bracket assembly is constrained to movement in a straight, substantially vertical path relative to the transom bracket assembly by the cooperation of interengaging ribs and recesses on the brackets. The brackets, which have their ribs on their outer faces and their recesses on their inner faces, can be formed from a single extrusion. Cross braces fit into the recesses on the inner faces of the brackets.
U.S. Pat. No. 5,964,627, which issued to Detwiler on Oct. 12, 1999, describes a variable height outboard motor mount. A manually adjustable outboard motor mount comprises two brackets. One is attachable to a boat transom and one is attachable to an outboard motor. The motor bracket is constrained to movement in a straight, substantially vertical path relative to the  transom bracket by the cooperation of rods on one bracket with spaced bearings in sleeves on the other bracket. The motor bracket is adjusted vertically by a shaft threaded into the transom bracket and rotatable in a combined thrust and journal bearing in the motor bracket. A nut on the threads of the shaft can be tightened against a plate of the transom bracket to lock the motor bracket against vertical movement. The nut has three radial arms disposed at 120 degree angles relative to one another to allow convenient manual tightening.
The patents described above are hereby expressly incorporated by reference in the description of the present invention.
Several problems are inherent in known types of jack plates. First, in order to remove the hydraulic components from a hydraulically powered jack plate, it is necessary to remove the outboard motor from the jack plate and disassemble the jack plate. In many cases, the removal of the outboard motor from the jack plate requires heavy lifting apparatus that is not available to many owners of marine vessels. In addition, known types of jack plates which incorporate hydraulic components can create undesirably high pressures within the hydraulic system when the jack plate reaches the end of its travel. In addition, known types of jack plates do not provide easily accessible means for the operator of a marine vessel to reduce the hydraulic pressure holding an outboard motor at a raised position. Furthermore, most known types of jack plates are sufficiently thick in a dimension extending rearwardly from the transom of a marine vessel that the outboard motor is supported at a location that is farther from the transom than is desirable in many applications.
It would therefore be significantly beneficial if a hydraulically powered jack plate could be provided that allows the operator of a marine vessel to disassemble the hydraulic components of the jack plate without having to remove the outboard motor from the jack plate. It would also be beneficial if a manually operable  pressure relief valve could be located at an easily accessible location within the jack plate structure. In addition, it would be beneficial if an automatically operable pressure relief valve could be provided that prevents excessive pressure build up within the hydraulic lines when the jack plate reaches its maximum limit of travel.